You somehow magically sense something there through your eyes, but you don’t see it at all. It’s stronger if you don’t look at it directly and move your head about a little. It’s like there’s an unconscious observer reporting where things are, and you just take the info and acknowledge it, but you don’t see it. Anyone else get this?
Above and beyond that, scientists say the rods of the eye are sensitive enough to detect individual photons.
I can’t confirm that myself, but it seems about right to me.